Shielded ignition manifold system



June 23, 1942- E. A. ROBERTSON SHIELDED IGNITION MANIFOLD SYSTEM Filed Aug. 10, 1935 ,l/IIIIIIIIIIII 'IIIIIII Patented June 23, 1942 SHIELDED IGNITION MANIFOLD SYSTEM Edwin'A. Robertson, Sandusky, Ohio, assignor,

by mesne assignments, to Bendix Aviation Corporation, South Bend, 11111., a corporation of Delaware Application August 10, 1935, Serial No. 35,683 3 Claims. (01. 114-74) This invention relates to ignition manifolds for internal combustion motors and has for a general object the provision of improvements in this art.

More particularly the invention relates to a manifold of the pull-in type which is shielded to prevent disturbance with radio reception by stray currents from the ignition wires housed therein.

Among the more specific objects of the invention are the provision of a manifold which can be readily assembled on a motor, for example, on an airship where space about the motor is very limited; which permits the insulated ignition wires to be pulled in easily and without injury to the insulating covering; which includes improved flexible sections whichwvill hold their cross-sectional shape even when bent and prevent the opening up of braided metal shielding placed thereon; and which in other respects constitutes an advance in the art.

The invention may be more readily understood by reference to the accompanying drawing of an illustrative embodiment thereof wherein:

Fig. l is an elevation view, partly in section and with parts broken away, showing a portion of a manifold embodying the present invention;

Fig. 2 is a section, partly in elevation taken on the line 2-2 of Fig. 1; a

Fig. 3 is a section taken on the line 3-3 of Fig. 1;

Fig. 4 is an enlarged section, partly in, elevation, of one end of a flexible trunk member; and a Fig. 5 is a similar view of a flexible branch member.

Referring to the drawing, there is shown in Fig. 1 a manifold assemblysometimes referred to as harness-which comprises some rigid sections and some flexible sections. Herein there are shown the curved rigid trunk sections 26, 21 united by the T-coupling 28. The manifold assembly is preferably connected with a magneto (not shown) by the flexible tube 3|. The assembly is connected with suitable parts at the spark plugs by flexible tubes 33.

Thus broadly, there is seen to be provided a manifoldhaving a number of separable parts which are so designed as to permit the convenientassembly thereof upon the motor as well as the convenient insertion therein of the insulated conductors.

The rigid tubular sections 26, 21, may be formed of any suitable metal which is a good electrical conductor and which has good abrasion resisting qualities. For example, a brass tube plated on the outside with cadmium has been found to be satisfactory.

At the points where the conductors emerge for the spark plugs (Figs. 1 and 3) the tube is pierced and pushed outward in smooth curvature to form nipples 34 over which the union fittings 35 are secured, as by soldering. It will be seen that the end of the nipples are disposed well back within an annular recess of the shell of the fitting 35 where they will not interfere with or injure the insulated conductors 30 when the latter are drawn therethrough.

In order to avoid excessive corona discharge and capacitance loss between the metal tube and the conductors it may be desirable to line the manifold with insulating material. Rubber may be used and one method of applying it which has given good results is to place a lining tube within the metal tube, expand it by pressure and cement it in place; or the rubber may be applied by a plating process. Another method which has proved satisfactory is to heat a cellulose tube-as, for example, by soaking it in hot water-until it softens somewhat, then toforce it into the metal tube and allow it to reharden in place. Such an insulating liner 36 is shown in Figs. 4 and 5. It may also be placed in the rigid metal members and couplings if desired.

For the sections which need to be flexible there is hereby provided a construction which insures that the cross-sectional shape will remain substantially constant. In the embodiment shown in Figs. 4 and 5 this construction includes a semiflexible inner loom tube 40 which has considerable strength against crushing. It may be formed by braiding a metal wire 4! such as steel or bronze with fibrous strands 42. The metal wire may run spirally to secure maximum rigidity. This tube may be impregnated with a material such as rubber or the like and may have a coat- 43 of the same or similar material on the outside to exclude water, oil and gasoline from the group of conductors inside. Upon this loom tube is braided the radio shielding jacket. This jacket may comprise a closely woven inner braid 44 of copper or other material which is a good electrical conductor and an outer braid 45 of an abrasionresisting material such as stainless steel. The combination of the loom tube of metal and fibrous strands and the metal shielding braidthereover Y is believed to have distinct advantages in that the braid can be wrapped tightly on the loom tube and the assembly can be bent freely without collapsing or changing in cross-sectional shape materially. This obviates the opening up of the shielding braid. The resilient coating 43 permits the braid to embed itself and assists in avoiding slippage and opening up of the braid. Unless the braid covers substantially the entire surface without openings it will not form a satisfactory shielding.

Instead of using the loom tube for a foundation there may be substituted one of the known types of spiral metal hose with sealed joints but in this case also there should be provided between the hose and the metal braid a coating of rubber or similar material which will not slip on the tube and in which the braid can embed itself to prevent its slipping and bunching and leaving open spaces when the assembly is flexed. Also an insulating liner may be used on the inside.

Couplings are provided at all joints permitting rapid assembly and removal. The rigid metal sections (Fig. 1) are provided with flanged collars 41 preferably sweated on with silver solder. The mating part is recessed interiorly to receive the end of the collar and is threaded exteriorly to i take a coupling nut 48. A metal gasket 49 (of lead or the like) is provided to make a tight joint and establish electrical continuity between the connected parts.

vided at all joints.

The couplings at the ends of the flexible sec-- tions also serve to hold the several concentric layers of material tightly together. The coupling for the trunk section is shown in Fig. 4 and for the branches in Fig. 5. They are not identical but correspond in the number and function ofparts so the description of one will serve for both.

An inner ferrule 50 and an outer ferrule 5i are placed on the inside and outside respectively of the tube assembly. The inner ferrule is then they may be lined with insulating material such as described above. This permits the insulated conductors to be readily pulled in and neatly dis- Similar metal gaskets are prov posed without sharp bends and without marring the insulation.

From the foregoing description it will be seen that the present invention provides a convenient and practical assembly which permits quick and easy insertion and removal of the conductors and which is effective'from the radio shielding and motor ignition standpoints.

While one embodiment has been described in detail to illustrate the principles of the invention, it will be understood that the invention may be variously altered and embodied within the scope of the subjoined claims.

I claim:

l. A shielding conduit for ignition wires or the like comprising a semi-flexible loom tube of interwoven metal wire and fibrous strands, a covering of yieidable moisture-proof material, such as rubber, surrounding and impregnating said tube, a braided jacket of metallic strips having good electrical conductivity, such as copper, surrounding and partially embedded in said yieldable coating, and a braided jacket of metallic strips, such as steel, having good abrasion-resisting qualities closely surrounding said first-named jacket.

. 2. A shielding conduit for ignition wires and the like comprising a semi-flexible loom tube of inter- .woven metal wire and fibrous strands, a covering of yieldable moisture-proof material, such as rubber, surrounding and having interlocking relation with said tube, a pair of superposed braided expanded, as by a boiler tube expander, to grip the tube assembly between itself and the outer ferrule. The ferrules are then secured and sealed together attheir outer ends by solder as shown at 52. The inner ferrule is flared at the outer end to provide easy threading of the insulated.

conductors through the manifold. It is j also flared out at its inner end to obviate having abrasive edges. flanges 53 for cooperating with the nuts 48 for joining the sections.

At intervals the manifold sections are secured to the motor by suitable bracketsi These also serve to ground the manifold assembly, ood electrical connections being made through them as by soldering, and prevent the building up of capacitancebetween the manifold and the metal work or the motor.

The "ii-coupling 28 is curved in the portion between the opposed open ends to conform to the curvature of the rigid metal tubes. Tne'portion leading the other opening is offset upward and turned ov r at an angle. The couplings are made smooth inside by sandblasting or otherwise. Or

The outer ferrules are providedwlth,

metallic jackets surrounding said coating, the inner jacket being partially embedded in said coating and having good electrical conductivity and the outer of said jackets having good abrasionresisting qualities, and a flexible lining of electrical insulating material inside and in close contact with said loom tube.

" 3. A shielding conduit for ignition wires and the like comprising a semi-flexible loom tube of interwoven metal wire and fibrous strands, a covering oi yieldable moisture-proof material, such as rubber, surrounding and having interlocking relation with said tube, a pair of superposed braided metallic jackets surrounding said coating, the inner jacket being partially embedded in said coating and having good electrical conductivity and the outerof said jackets having good abrasion-resisting qualities, and a ferrule in' an end of said conduit comprising a rigid metallic sleeve surrounding said end and a metallic sleeve expanded within said end of the conduit to compress the latter between said sleeves, the enter end of said second named sleeve being flared outwardly and secured to said first-named sleeve, as by soldering.

EDWIN A. ROBERTSON. 

